How to add a tab next to "Add Data" in the workbench

[mdchuc]

I have installed TerriaJS 7.11.16 on my local machine and it is working great.
Now I wanted to modified the workbench to include an additional tab next to the "Add Data" tab.
This new tab is intended for requesting long-running processing on the server side (such as Cesium task).
I attached an image of the prototype UI.

My questions are:

1. Where in the code should I look for in order to make the change?
   Is that possible to use Catalog Functions in the new tab as a way to trigger a generic RestAPI (such as running task in server with Celery).
2. Is this a proper use of TerriaJS?